Copper base alloy having wear resistance at high temperatures

ABSTRACT

The present invention relates to copper base alloys having excellent seizure resistance and wear resistance at high temperatures containing copper as the principal constituent, and zinc (Zn), aluminum (Al), manganese (Mn), silicon (Si), chromium (Cr), and phosphorus (P) as alloy elements.

United States Patent [1 1 Niimi et al.

COPPER BASE ALLOY HAVING WEAR RESISTANCE AT HIGH TEMPERATURES [76] Inventors: Itaru Niimi, 4-1205, Obasama, Aza,

Filed:

Takabari, Ooaza, Idaka-cho, Chigusa-ku, Nagoya City, Aichi Prefecture; Yasuhisa Kaneko, 10, Toyota-c110, Toyota City; Yoshiro Komiyama; Yoshiki Uchiyama, both of 48, 4-chome, Heiwa-cho, Toyota City; Yasuo Takeda, 8, Toyota-cho,

Toyota City; Shirou Maeda, l2, 6-chome, Miyukihon-machi, Toyota City, all of Japan Aug. 31, 1971 Appl. No.: 176,577

Foreign Application Priority Data Dec. 28, 1970 Japan 45/120195 US. Cl 75/l57.5, 75/153, 75/156.5,

75/157, 123/188 AA Int. Cl. C22c 9/10, C22c 9/04 Field of Search 75/157.5, 160, 161,

75/162, 153; 148/32; 123/188 A, 188 AA,

[ Nov. 20, 1973 OTHER PUBLICATIONS The Automobile Engineer, January 1935, pages 23 & 24

Primary Examiner-Charles N. Lovell Attorney-Arthur G. Connolly et a].

[57] ABSTRACT The present invention relates to copper base alloys having excellent seizure resistance and wear resistance at high temperatures containing copper as the principal constituent, and zinc (Zn), aluminum (Al), manganese (Mn), silicon (Si), chromium (Cr), and phosphorus (P) as alloy elements;

4 Claims, 1 Drawing Figure COPPER BASE ALLOY HAVING WEAR RESISTANCE AT HIGH TEMPERATURES BACKGROUND OF THE INVENTION The present invention relates to copper base alloys, and more particularly to copper base alloys that have significant wear resistance at elevated temperatures.

Alloys having excellent wear resistance at high temperatures have long been sought as materials for parts subjected to considerable frictional loads at high temperatures. For example, exhaust valve seat materials commonly used today for four cycle automobile engines include cast iron, special cast iron, heat resisting steel and the like. However, these alloys have the disadvantage that when lead-free gasoline, LPG (liquefied propane gas), etc., are used as fuel, they are subject to an unusual wear, lowering of the output of the internal combustion engine, or deterioration of exhaust gas (increase of CO or hydrocarbon). Trouble-free use of these alloys over long periods of time is therefore impossible.

After numerous studies made heretofore for the purpose of ameliorating the above-mentioned disadvantages, the inventors of the present invention have found that copper base alloys containing zinc, manganese, silicon, chromium and phosphorous and the like as alloy elements, are excellent in wear resistance at high temperatures.

SUMMARY OF THE INVENTION The present invention relates to copper base alloys excellent in seizure resistance and wear resistance at high temperatures. These alloys are composed of elements within specific composition ranges.

The alloys according to the present invention are copper base alloys having high wear resistance at high temperatures containing copper as a principal constituent, and from 25 to 40 percent zinc, from .1 to 8 percent aluminum, from 1 to percent manganese, from 0.3 to 2.0 percent silicon, from 0.8 to 3 percent chromium, and from 0.3 to 1 percent phosphorus, and may further contain a small quantity of other elements. (All percentages mentioned in the specification represent weight percent.)

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing is a microscopic photograph showing the compositon of the alloy A according to the Example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The copper base alloys according to the present invention are alloys which contain copper as the principal constituent, and zinc, aluminum, .manganese, silicon, chromium and phosphrous as alloy elements, and further may contain a small quantity of other elements.

The alloys according to the present invention are suitable as fabricating materials for exhaust valve seats used in internal combustion engines, particularly the type that uses lead-free gasoline, LPG, or the like which does not contain additives such as lead. When the alloy of the present invention is used as a valve seat material, the frictional load is reduced to a negligible quantity. Also, high engine revolutions and high loads and operation during a long engine run can be effected without any difficulty. Further, the alloys according to the present invention are also suitable as fabricating materials for components used in a region where dry wear resistance at high temperatures is required, for example, valve-stem guides, synchronizer rings and bearing constructions.

The effect and the reason for each constituent element of the alloys according to the present invention are as follows.

Among the elements of the alloys according to the present invention, copper is the principal constituent. It has excellent heat conductibility and anticorrosiveness, and combines with oxygen in the air at high temperatures to form copper oxide. A thin film of this copper oxide produces self-lubricating action thereby contributing to the increase of wear resistance of the alloy. Zinc dissolves into copper as a solid solution, reinforcing the crystal matrix, and combines as high temperature with oxygen in the air to produce zinc oxide. This thin film of zinc oxide also produces selflubricating action and remarkably ameliorates the wear resistance of the alloy. Further, zinc lowers the melting point of alloy and ameliorates its castability. Accordingly, when the reinforcement of the crystal matrix and the castability of alloy is taken into consideration, it is desirable that the content of zinc be more than 25 percent. On the other hand, with more than 40 percent zinc, the machinabilty of the alloy is reduced when zinc coexists with other elements which contribute to the reinforcement of the crystal matrix and the wear resistance. Hence, the content of zinc has been determined to be less than 40 percent. Aluminum reinforces the crystal matrix and ameliorates the wear resistance, but since this reinforcement is low in degree, with less than 1 percent aluminum the content of zinc has been determined to be more than 1 percent. However, with more than 8 percent aluminum the machinability deteriorates when it coexits with chromium and the content of aluminum is determined to be less than 8 percent.

Chromium reinforces the crystal matrix and increases the hardness equally as aluminum. It also contributes to the amelioration of wear resistance. However, with less than 0.8 percent chromium, the effect of aluminum is small, and the content of chromium has been determined to be more than 0.8 percent. Further, with more than 3 percent chromium, the machinability of the alloy decreases, and the content of chromium has been determined to be less than 3.0 percent. As for manganese, it reinforces the crystal matrix in the same manner as in the case of aluminum, and ameliorates the wear resistance, producing at the same time a remarkably hard intermetallic compound conjointly with silicon. This intermetallic compound I is uniformly dispersed in a finely divided state in the crystal matrix thereby remarkably ameliorating the wear resistance. With less than 1 percent manganese, the quantity of intermetallic compound produced conjointly with siliconis small and the contribution to the wear resistance is small. Thus, the content of manganese has been determined to be more than 1 percent. With more than 5 percent manganese, the machinability of the alloy is decreased due to coexistence of manganese with zinc, aluminum, silicon, chromium and the like. Thus, the content of manganese is determined to be less than 5 percent.

As for silicon, although it produces a remarkably hard intermetallic compound conjointly with manganese and contributes to the increase of wear resistance of the alloy, the quantity produced of hard intermetal- 3 4 lic compound conjointly with manganese is small and g g; the contribution to the wear resistance is small when 01% the content of silicon is less than 0.3 percent. Hence, Ti 03 the content of silicon has been determined to be more w 03% arena;

Wear Tensile Hardquanstrength ness tity Chemical content (wt. percent) (kg/cm?) Hv (10) (111111.)

Ordinary cast iron SAE G 4500- 30 240 8.35 Control specimen:

Special cast iron C 3.4, Si 2.4, Mn 0.76, P 0.3, Cr 0.6, M 0.7, V 0.15, Fe the rest 40 280 6. 36 Heat resisting steel- C 0.8, Si 2.3, S 0.1, C! 20, N1 1.3, Fe the rest 100 300 2. 70 Alloy of the invention:

A (See Table 1) 68 230 0.25 (See Table 1). 70 260 0. 40

than 0.3 percent. Also, with more than 2.0 p con, the machinability of the alloy is lowered due to the coexistence of zinc, aluminum, manganese, chromium and the like. The content of silicon is determined to be less than 2 percent.

Phosphorus is used as a deoxidizer, and with more than 0.3 percent phosphorus it tends to increase the hardness of the alloy and also contribute to the amelioration of wear resistance. However, when the phosphorus content is more than 1 percent, the machinability of alloy decreases. Therefore, the content of phosphorus is determined to be less than 1 percent.

Further, when the content of iron or nickel is less than 2%, Sn, Pb, Ti, Zr, Be, B, Co, or W is less than 1 percent, and the total sum of these elements is less than 5 percent, the performance of the alloy in the construction of valve seats, valve-stem-guides, synchronizer rings and bearings is not adversely affected, and these elements may be added, if desired.

The present invention is described below with reference to a specific example.

Two specimens of alloy according to the present invention having the compositions as shown in Table l have been prepared, and tests of sliding friction at high temperatures have been effected. The control specimens include conventional ordinary cast iron, special cast iron, and heat resisting steel. The test results concerning the properties and the friction of each alloy are shown in Table 2.

TABLE 1 Composition of the alloy B according to the present invention Composition of the alloy A according to the present invention The determination of the was; quantity mentioned 7 above has been effected by fixing an annular specimen that had been heated to 400450C. in an aluminum alloy, rotating it 10 times per minute, imparting by means of a jig made of heat resisting steel repetitive shocks with collision velocity of 0.2m/sec., surface pressure of 30 Kg/cm, and 2,500 turns/min, and determining the variations of thickness of the specimens for a determined period.

From the above-mentioned test results it is understood that the alloys according to the present invention have extremely excellent wear resistance when compared with ordinary cast iron, special cast iron and heat resisting steel. The alloys of the present invention are particularly suitable for fabricating exhaust valve seats which are exposed to extremely high temperatures of the four cycle engines for automobiles which use leadfree gasoline and LPG as fuel.

What is claimed is:

l. A copper base alloy having wear resistance at high temperature consisting essentially of 25 to 40 percent zinc, l to 8 percent aluminum, 1 to 5 percent manganese, 0.3 to 2.0 percent silicon, 0.8 to 3.0 percent chromium, and 0.3 to 1.0 percent phosphorus, and the balance copper.

2. A copper base alloy as in claim 1 including additional elements of less than 2 percent of any element selected from the group consisting of iron and nickel, less than 1 percent of any element selected from the group consisting of tin, lead, titanium, zirconium, beryllium, boron, cobalt and tungsten and wherein the total sum of said additional elements is less than 5 percent.

3. A valve seat of an internal combustion engine fabricated of the alloy according to claim 1.

4. A valve seat of an internal combustion engine fabricated of the alloy according to claim 6.

* l IR 

2. A copper base alloy as in claim 1 including additional elements of less than 2 percent of any element selected from the group consisting of iron and nickel, less than 1 percent of any element selected from the group consisting of tin, lead, titanium, zirconiuM, beryllium, boron, cobalt and tungsten and wherein the total sum of said additional elements is less than 5 percent.
 3. A valve seat of an internal combustion engine fabricated of the alloy according to claim
 1. 4. A valve seat of an internal combustion engine fabricated of the alloy according to claim
 6. 